Method and Apparatus for Channelizing Sampled Broadband Signal

ABSTRACT

A system for isolating individual channels in a broadcast signal is provided. The system includes a plurality of multipliers, each having an input and an output. A summer coupled to the outputs of each of the plurality of multipliers is provided to generate an output. A multiplication factor system provides a multiplication factor to each of the multipliers to select a predetermined frequency channel of the input signal.

FIELD OF THE INVENTION

The invention relates to reception and processing of broadband signals,and more specifically to a method and apparatus for channelizing asampled broadband signal that does not require the signal to bedown-mixed.

BACKGROUND OF THE INVENTION

In order to extract a channel of data from a broadband signal, it isnecessary to down-mix the received broadband signal, to filter thesignal, and to perform other processing to isolate the desired channel.Where the broadband signal is digitally processed, the samplingfrequency may be much greater than the desired signal processingfrequency, such that decimation of the sampled data is also required.These processes add cost to the signal processing circuitry and increasethe power consumption requirements for the signal processing circuitry.

SUMMARY OF THE INVENTION

The current invention provides an apparatus and method forchannelization of a broadband signal that does not require mixing,filtering or decimation of the received signal.

In accordance with an exemplary embodiment of the present invention, asystem for isolating individual channels in a broadband signal isprovided. The system includes a plurality of multipliers, each having aninput and an output. A summer coupled to the outputs of each of theplurality of multipliers is provided to generate an output. Amultiplication factor system provides a multiplication factor to each ofthe multipliers to select a predetermined frequency channel of the inputsignal.

Those skilled in the art will further appreciate the advantages andsuperior features of the invention together with other important aspectsthereof on reading the detailed description that follows in conjunctionwith the drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a diagram of a system for channelization of a broadband signalin accordance with an exemplary embodiment of the present invention;

FIG. 2 is a diagram of time domain samples and associated frequencydomain spectrums in accordance with an exemplary embodiment of thepresent invention; and

FIG. 3 is a diagram of method for channelization of a broadband signalin accordance with an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the description that follows, like parts are marked throughout thespecification and drawings with the same reference numerals,respectively. The drawing figures might not be to scale, and certaincomponents can be shown in generalized or schematic form and identifiedby commercial designations in the interest of clarity and conciseness.

FIG. 1 is a diagram of a system 100 for channelization of a broadbandsignal in accordance with an exemplary embodiment of the presentinvention. System 100 can be implemented in hardware, software or asuitable combination of hardware and software, and can be one or morediscrete hardware systems. As used herein, “hardware” can include acombination of discrete components, an integrated circuit, anapplication-specific integrated circuit, a field programmable gatearray, a digital signal processor, or other suitable hardware. As usedherein, “software” can include one or more objects, agents, threads,lines of code, subroutines, separate software applications, two or morelines of code or other suitable software structures operating in two ormore software applications or on two or more processors, or othersuitable software structures. In one exemplary embodiment, software caninclude one or more lines of code or other suitable software structuresoperating in a general purpose software application, such as anoperating system, and one or more lines of code or other suitablesoftware structures operating in a specific purpose softwareapplication.

System 100 includes receiver 102, which receives a broadband signal andperforms suitable processing on the broadband signal. In one exemplaryembodiment, receiver 102 can amplify the broadband signal, can samplethe broadband signal at a suitable sampling frequency, and can performother suitable processing.

Receiver 102 is coupled to switch 104. As used herein, the term“coupled” and its cognate terms such as “couples” or “couple,” caninclude a physical connection (such as a wire, optical fiber, or atelecommunications medium), a virtual connection (such as throughrandomly assigned memory locations of a data memory device or ahypertext transfer protocol (HTTP) link), a logical connection (such asthrough one or more semiconductor devices in an integrated circuit),other suitable connections, or a suitable combination of connections. Inone exemplary embodiment, switch 104 receives a series of digitalsamples from receiver 102, and provides the samples in a predeterminedorder to multipliers 106A through 106N. Other suitable processes canalso or alternatively be used, such as where switch 104 receives ananalog signal and multipliers 106A to 106N perform analog to digitalprocessing of the signal.

Multipliers 106A through 106N apply a predetermined multiplicationfactor to the signal provided by switch 104. In one exemplaryembodiment, multiplication factor system 108 can provide multiplicationfactors to multipliers 106A through 106N based on a channel selectionreceived from channel selection system 110 or other suitable systems.Likewise, multipliers 106A through 106N can have a predeterminedmultiplication factor, such as where system 100 is used for extracting asingle predetermined channel from a broadband signal, or other suitableprocesses can also or alternatively be used.

Channel selection system 110 allows a channel of a broadband signal tobe selected, such as based on a predetermined frequency band ofinterest. In one exemplary embodiment, channel selection system 110 canpresent user-selectable channel data, can receive control data thatidentifies or is correlated to a channel of data in a broadband datasignal, or other suitable processes can also or alternatively be used.

Multiplication factor system 108 receives channel data from channelselection system 110 or other suitable systems and generatesmultiplication factor data for multipliers 106A through 106N. In oneexemplary embodiment, multiplication factor system 108 can store alook-up table of multiplication factors associated with predeterminedchannels, can generate multiplication factors based on channel data,such as bandwidth data and center band data, or can perform othersuitable processes. In another exemplary embodiment, multiplicationfactor system 108 can receive decimation data that identifies adown-sampling ratio, such as where the number of multipliers can bevaried, the sampling rate of receiver 102 can be varied, or in othersuitable manners. In this exemplary embodiment, the multiplicationfactors generated by multiplication factor system 108 can be coordinatedwith the sampling frequency and the decimation data so as to generate anoutput signal at a predetermined sample rate.

Summer 112 receives the multiplied outputs from multipliers 106A through106N and sums the outputs to generate a channelized output signal at alower sampling rate than the sampling rate of the received broadbandsignal. As discussed below, by selecting suitable multiplication factorsfor the time domain samples and adding the adjusted samples to form asingle sample, the effect in the frequency domain is the same assampling at a higher frequency, and can be used to select frequencybands of interest or channels without the need to down-mix, filter ordecimate the sampled data.

In operation, system 100 channelizes a broadband signal without the needfor mixers, filters, decimators or other common signal processingcomponents. System 100 can be used in a suitable broadband receiver,such as a cable or satellite receiver, a wireless card for a notebookpersonal computer, a cellular telephone, a hand-held computing device,navigational devices, telecommunication devices, televisions, radios, orother suitable devices utilizing receivers. In addition, system 100 canbe used to detect and compensate for timing jitter.

FIG. 2 is a diagram 200 of time domain samples and associated frequencydomain spectrums in accordance with an exemplary embodiment of thepresent invention. Time domain samples 202 at a sampling time period ofT1 can be transformed in the frequency domain to frequency bands A1, A2and A3 of frequency spectrum 204, having a separation frequency F1,which equals 1/T1. If the time domain samples are separated into oddtime domain samples 206 and even time domain samples 210, the associatedfrequency spectrums 208 and 212 will include frequency bands A1, A2 andA3, as well as frequency bands D1 and D2, each having a separationfrequency of F2, which equals 1/T2. Because time domain samples 202 arethe sum of time domain samples 206 and 210, frequency spectrum 204 canbe generated by subtracting frequency bands D1 and D2 from frequencyspectrums 208 and 212. By applying suitable multiplication factors totime domain samples 206 and 210, channelization of the associatedfrequency domain spectrum can be accomplished.

FIG. 3 is a diagram of method 300 for channelization of a broadbandsignal in accordance with an exemplary embodiment of the presentinvention. Method 300 begins at 302, where a channel selection isreceived. In one exemplary embodiment, the channel selection can be apredetermined frequency channel, can be a frequency band, or othersuitable selections can be used. The method then proceeds to 304.

At 304, multiplication coefficients for the selected channel are set. Inone exemplary embodiment, the multiplication coefficients can beobtained from a look-up table, can be calculated based on the samplerate and frequency channel data, or other suitable processes can beused. The method then proceeds to 306.

At 306, a broadband signal is sampled in the time domain. In oneexemplary embodiment, a received and amplified signal can be sampled ata predetermined sampling frequency, the sampling frequency can be setbased on the selected channel, or other suitable processes can also oralternatively be used. The method then proceeds to 308.

At 308, the samples are provided to multipliers that utilize themultiplication coefficients. In one exemplary embodiment, the samplescan be provided in a predetermined order, and the multiplied samplevalues can be stored. The method then proceeds to 310.

At 310, the multiplier outputs are summed, such as by adding themultiplied sample values from each multiplier, by storing the multipliedsample values until a complete set of samples is obtained, or in othersuitable manners. The sum is then output at a sample rate that is lowerthan the input sample rate by a factor related to the number ofmultipliers. The method then proceeds to 312.

At 312, it is determined whether a change in channel is required. In oneexemplary embodiment, the change in channel can be received as acontrol, can be performed based upon predetermined channel selectiondata, or can be performed in other suitable manners. If it is determinedthat a change in channel is required, the method returns to 302,otherwise the method proceeds to 314.

At 314, it is determined whether a change in the output sample rate isrequired. In one exemplary embodiment, sample rate control data can bereceived to change the sample rate of the output signal, predeterminedsample rate selection data can be used, or other suitable processes canalso or alternatively be used. If it is determined that a change in thesample rate is required, the method proceeds to 316, where the number ofmultipliers, the sample rate of the input samples, the multiplicationcoefficients, or other suitable variables are adjusted to generate datafor the selected frequency channel at the selected sample rate. Themethod then returns to 302. Otherwise, the method returns to 306.

In operation, method 300 allows a broadband signal to be sampled andprocessed to select a channel of data without the need for down-mixing,filtering and decimation. Method 300 can be used to selectedpredetermined or adjustable frequency channels in a broadband signalwithout the need to change oscillator frequencies, decimators, or otherparameters.

Although exemplary embodiments of an apparatus of the present inventionhave been described in detail herein, those skilled in the art will alsorecognize that various substitutions and modifications can be made tothe apparatus without departing from the scope and spirit of theappended claims.

1. A system for isolating individual channels in a broadband signalcomprising: a plurality of multipliers, each having an input and anoutput; a summer coupled to the outputs of each of the plurality ofmultipliers to generate an output; and a multiplication factor system toprovide a multiplication factor to each of the multipliers to select apredetermined frequency channel of the input signal.
 2. The system ofclaim 1 further comprising a switch coupled to each of the multipliers,wherein the switch selects one of the multipliers so as to provide aninput signal to the selected multiplier.
 3. The system of claim 1wherein each multiplier can process a digital signal.
 4. The system ofclaim 2, wherein the switch can select a different multiplier for eachone of a succession of digital samples.
 5. The system of claim 4 whereina sample rate of the output can be less than a sample rate of an inputsignal.
 6. The system of claim 1 further comprising a channel selectorsystem to generate the multiplication factor for the multiplicationfactor system.
 7. The system of claim 1 further comprising a receiver toreceive a signal and generate an input signal by sampling the receivedsignal at a sampling frequency.
 8. A method for isolating individualchannels in a broadband signal comprising: multiplying a received signalwith a plurality of multipliers, each multiplier having an associatedmultiplication factor; summing the outputs of the multipliers; andgenerating an output signal representing a frequency band of thereceived signal from the summed multiplier outputs.
 9. The method ofclaim 8 further comprising switching the received signal from a firstmultiplier to a second multiplier.
 10. The method of claim 8 furthercomprising: converting the received signal into a sequence of digitalsamples; and wherein multiplying the received signal with the pluralityof multipliers comprises providing successive digital samples todifferent multipliers.
 11. The method of claim 8 further comprising:receiving channel selection data; and generating the multiplicationfactors in response to the channel selection data.
 12. The method ofclaim 8 wherein generating the output signal representing the frequencyband of the received signal from the summed multiplier outputs furthercomprises generating the output signal at a lower sample rate than asample rate of the received signal.
 13. An apparatus for isolatingindividual signals in a broadband signal comprising: means formultiplying each of a plurality of inputs by a corresponding scalingfactor; means for summing the multiplied plurality of signals togenerate an output; and wherein the scaling factors applied to theinputs select a predetermined channel of a signal.
 14. The apparatus ofclaim 13 further comprising means for providing a sequence of samples tothe means for multiplying each of the plurality of inputs by thecorresponding scaling factor.
 15. The apparatus of claim 13 wherein theplurality of inputs comprises a digital signal.
 16. The apparatus ofclaim 14, wherein the plurality of inputs comprises a series of digitalsamples and comprising a switch for selecting one of a plurality ofdifferent multipliers for each successive digital sample.
 17. Theapparatus of claim 16 wherein a sample rate of the output can be lessthan a sample rate of the series of digital samples.
 18. The apparatusof claim 13 further comprising means for generating the scaling factorsin response to channel selection data.
 19. The apparatus of claim 13further comprising means for receiving a signal and generating theplurality of inputs.